The invention relates to power-driven conveyors and, more particularly, to modular conveyor belts constructed of rows of belt modules hingedly interlinked end-to-end by hinge pins.
Conventional modular conveyor belts and chains are made up of modular links, or belt modules, arranged in rows. Spaced apart link ends extending from each end of the modules include aligned apertures. The link ends along one end of a row of modules are interleaved with the link ends of an adjacent row. A pivot rod, or hinge pin, journalled in the aligned apertures of the end-to-end-connected rows, connects adjacent rows together to form an endless conveyor belt capable of articulating about a drive sprocket.
In many industrial applications, articles are allowed to accumulate on a continuously moving conveyor belt before being off-loaded. Friction between the conveying surface of the moving belt and the accumulated articles causes the articles to push against each other increasing backline pressure. Backline pressure can cause damage to the articles, excessively load the conveyor belt and its drive components, and accelerate belt wear. Rotatable elements, such as rollers, in rolling contact with the undersides of conveyed articles have been used to reduce friction and lower backline pressure.
In other conveyor applications, articles must be pushed off the side of a constantly moving or stop-and-go conveyor belt. Rollers oriented with their axes of rotation in the direction of belt travel have been used to provide low friction rolling contact with the undersides of conveyed articles being pushed off the side of a conveyor.
Arscott U.S. Pat. No. 4,231,469, issued Nov. 4, 1980, discloses a conveyor comprising a plurality of interconnected cradles and a rotatable member mounted in each cradle. The rotatable members extend above the respective cradle for rolling contact with an object placed on the conveyor to allow the objects to move relative to the conveyor. The Arscott patent discloses rotatable members with axes of rotation in the direction of belt travel for side off-loading and perpendicular to the direction of belt travel for low backline pressure.
One shortcoming of the Arscott conveyor and other roller-top belts is that they are difficult to clean owing to the many surfaces and nooks and crannies associated with the rollers. Cleanability is especially important in some industries, such as meat-handling, where bacteria can form in and spread from difficult-to-clean areas.
Another shortcoming of many low backline pressure conveyors is the placement of a roller on the pivot rod. Such a placement requires fewer or thinner link ends resulting in less belt pull strength or narrow rollers resulting in high contact pressure on conveyed articles. Thus, there is a need for a modular conveyor belt that features low backline pressure or low-friction side transfer and that is easy to clean.
These needs and others are satisfied by the invention, which provides a modular roller-top conveyor belt. The belt is constructed of a series of rows of belt modules having hinge elements at opposite ends of each row. The hinge elements of one row are interleaved with the hinge elements of an adjacent row. Hinge pins interlink the interleaved hinge elements of adjacent rows to form an endless conveyor belt with pivotable joints between each row. Each row is constructed of one or more belt modules. Each module includes a body section extending between first and second ends in the direction of belt travel. The body section includes a bottom surface and an opposite upper deck that forms an upper surface. At least one cavity is formed in the body section of one or more of the modules. The cavity opens onto the upper surface. A roller residing in the cavity engages conveyed articles in rolling, low-friction contact.
In various versions of the belt of the invention, the rollers are cylinders for rotation about axes parallel to or perpendicular to the direction of belt travel or balls for omnidirectional rotation.
In one version of the belt of the invention, the cavity extends from the upper surface completely through the body section to an opening in the bottom surface to allow debris to fall through. In another version, the belt has a transverse drive element extending from the bottom surface and the cavity does not extend through the drive element to allow for placement of drive sprockets across the entire width of the belt row.
In versions with a cylindrical roller, the belt includes an axle that fits through a central bore in the roller. Opposite walls of the cavity have collinear holes to support the ends of the axle. In a version having more than one cavity in the body section, the collinear holes can be extended to join the cavities and form a passageway along a transverse axis to admit a single axle on which all the rollers ride. The roller can be made of a rubber material with its bore lined by a bushing to receive the axle. In a version designed for side transfer of articles, at least one of the collinear holes opens into a gap between consecutive hinge elements for easy insertion of the axle during module construction. As the belt is put together, the axle is retained in the holes by an interleaved hinge element of an adjacent belt row disposed in the gap. To guide articles that drop onto the conveyor on an edge or otherwise skewed orientation, another version of the belt of the invention features an upwardly sloping, for example, convex, upper surface. The upper surface rises from the first and second ends of the belt rows toward the roller. This construction tends to guide the skewed article into a conveying position atop the roller. A version with a pivotable support mounted in the cavity and a roller and axle rotatably supported in the support provides a caster-like action that gives the rollers the versatility to roll in all directions.
In one version of the belt of the invention for use with roller balls, the cavity includes a recessed surface that supports bearing elements, which provide low-friction bearing surfaces for the ball. The bearings elements are ridges rising from the recessed surface of the cavity. In another version, the bearing elements include a plurality of ball bearings in a ball bearing holder. A cover has a circular aperture with a diameter less than the diameter of the ball to retain it in the cavity with just a portion of the ball protruding above the surface of the cover into rolling contact with conveyed articles. The cover can be integrally molded with the upper deck to engage retention structure on the upper deck in snap-fit retention. In one integrally molded version, the cover includes a lip defining the circular aperture whose diameter is adjustable by deformation, for example, from a first diameter to a second diameter. The first diameter is greater than the diameter of the ball to allow the ball to be installed in the cavity. The second diameter is less than the diameter of the ball to retain the ball in the cavity with a portion of the ball protruding through the cover into rolling contact with conveyed articles. In another version, the cover has sloping sides to guide askew articles into position atop the roller balls.